Halogen additives, such as those based on fluorine, chlorine, and bromine, have been used to give flame retardant properties to TPU compositions. In recent years, certain end use applications are specifying that the TPU composition be halogen free. This has required TPU formulators to search for other flame retardants to replace the previously used halogen additives.
U.S. Patent Application Publication No. US 2005/0011401 discloses an elastic floor covering material which comprises a phosphinate salt or a diphosphinate salt as a flame retardant.
U.S. Pat. No. 6,777,466 issued to Eckstein, et al. discloses the use of melamine cyanurate as the only organic flame retardant additive in a TPU composition.
U.S. Pat. No. 6,547,992 issued to Schlosser et al. discloses a flame retardant combination including certain phosphinate and/or diphosphinate components and a synthetic inorganic compound and/or a mineral product. Additionally, the disclosed flame retardant combination may include nitrogen-containing components.
U.S. Pat. No. 6,365,071 issued to Jenewein et al. discloses a flame retardant combination for thermoplastic polymers including certain phosphinate and/or diphosphinate components and certain nitrogen-containing components.
U.S. Pat. No. 6,509,401 issued to Jenewein et al. discloses a flame retardant combination including certain phosphorus-containing components and certain nitrogen-containing components for thermoplastic polymers.
U.S. Pat. No. 6,255,371 issued to Schlosser et al. discloses a flame retardant combination including certain phosphinate and/or diphosphinate components in combination with certain components derived from melamine.
U.S. Pat. No. 6,207,736 issued to Nass et al. discloses a flame retardant combination including certain phosphinic acid salts and/or diphosphinic acid salts and certain nitrogen-containing phosphate components.
Still, there exists a need in the art for effective non-halogenated flame retardant combinations that impart flame retardant characteristics to thermoplastic polyurethane compositions while not impairing mechanical strength and processability.